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259 lines
6.3 KiB
259 lines
6.3 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* x86 FPU boot time init code: |
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*/ |
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#include <asm/fpu/internal.h> |
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#include <asm/tlbflush.h> |
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#include <asm/setup.h> |
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#include <linux/sched.h> |
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#include <linux/sched/task.h> |
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#include <linux/init.h> |
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/* |
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* Initialize the registers found in all CPUs, CR0 and CR4: |
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*/ |
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static void fpu__init_cpu_generic(void) |
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{ |
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unsigned long cr0; |
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unsigned long cr4_mask = 0; |
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if (boot_cpu_has(X86_FEATURE_FXSR)) |
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cr4_mask |= X86_CR4_OSFXSR; |
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if (boot_cpu_has(X86_FEATURE_XMM)) |
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cr4_mask |= X86_CR4_OSXMMEXCPT; |
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if (cr4_mask) |
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cr4_set_bits(cr4_mask); |
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cr0 = read_cr0(); |
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cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */ |
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if (!boot_cpu_has(X86_FEATURE_FPU)) |
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cr0 |= X86_CR0_EM; |
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write_cr0(cr0); |
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/* Flush out any pending x87 state: */ |
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#ifdef CONFIG_MATH_EMULATION |
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if (!boot_cpu_has(X86_FEATURE_FPU)) |
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fpstate_init_soft(¤t->thread.fpu.state.soft); |
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else |
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#endif |
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asm volatile ("fninit"); |
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} |
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/* |
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* Enable all supported FPU features. Called when a CPU is brought online: |
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*/ |
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void fpu__init_cpu(void) |
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{ |
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fpu__init_cpu_generic(); |
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fpu__init_cpu_xstate(); |
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} |
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static bool fpu__probe_without_cpuid(void) |
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{ |
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unsigned long cr0; |
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u16 fsw, fcw; |
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fsw = fcw = 0xffff; |
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cr0 = read_cr0(); |
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cr0 &= ~(X86_CR0_TS | X86_CR0_EM); |
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write_cr0(cr0); |
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asm volatile("fninit ; fnstsw %0 ; fnstcw %1" : "+m" (fsw), "+m" (fcw)); |
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pr_info("x86/fpu: Probing for FPU: FSW=0x%04hx FCW=0x%04hx\n", fsw, fcw); |
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return fsw == 0 && (fcw & 0x103f) == 0x003f; |
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} |
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static void fpu__init_system_early_generic(struct cpuinfo_x86 *c) |
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{ |
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if (!boot_cpu_has(X86_FEATURE_CPUID) && |
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!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) { |
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if (fpu__probe_without_cpuid()) |
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setup_force_cpu_cap(X86_FEATURE_FPU); |
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else |
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setup_clear_cpu_cap(X86_FEATURE_FPU); |
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} |
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#ifndef CONFIG_MATH_EMULATION |
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if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_FPU)) { |
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pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n"); |
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for (;;) |
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asm volatile("hlt"); |
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} |
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#endif |
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} |
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/* |
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* Boot time FPU feature detection code: |
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*/ |
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unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu; |
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EXPORT_SYMBOL_GPL(mxcsr_feature_mask); |
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static void __init fpu__init_system_mxcsr(void) |
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{ |
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unsigned int mask = 0; |
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if (boot_cpu_has(X86_FEATURE_FXSR)) { |
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/* Static because GCC does not get 16-byte stack alignment right: */ |
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static struct fxregs_state fxregs __initdata; |
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asm volatile("fxsave %0" : "+m" (fxregs)); |
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mask = fxregs.mxcsr_mask; |
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/* |
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* If zero then use the default features mask, |
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* which has all features set, except the |
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* denormals-are-zero feature bit: |
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*/ |
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if (mask == 0) |
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mask = 0x0000ffbf; |
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} |
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mxcsr_feature_mask &= mask; |
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} |
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/* |
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* Once per bootup FPU initialization sequences that will run on most x86 CPUs: |
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*/ |
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static void __init fpu__init_system_generic(void) |
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{ |
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/* |
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* Set up the legacy init FPU context. (xstate init might overwrite this |
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* with a more modern format, if the CPU supports it.) |
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*/ |
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fpstate_init(&init_fpstate); |
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fpu__init_system_mxcsr(); |
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} |
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/* |
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* Size of the FPU context state. All tasks in the system use the |
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* same context size, regardless of what portion they use. |
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* This is inherent to the XSAVE architecture which puts all state |
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* components into a single, continuous memory block: |
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*/ |
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unsigned int fpu_kernel_xstate_size; |
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EXPORT_SYMBOL_GPL(fpu_kernel_xstate_size); |
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/* Get alignment of the TYPE. */ |
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#define TYPE_ALIGN(TYPE) offsetof(struct { char x; TYPE test; }, test) |
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/* |
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* Enforce that 'MEMBER' is the last field of 'TYPE'. |
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* |
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* Align the computed size with alignment of the TYPE, |
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* because that's how C aligns structs. |
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*/ |
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#define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \ |
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BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \ |
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TYPE_ALIGN(TYPE))) |
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/* |
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* We append the 'struct fpu' to the task_struct: |
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*/ |
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static void __init fpu__init_task_struct_size(void) |
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{ |
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int task_size = sizeof(struct task_struct); |
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/* |
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* Subtract off the static size of the register state. |
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* It potentially has a bunch of padding. |
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*/ |
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task_size -= sizeof(((struct task_struct *)0)->thread.fpu.state); |
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/* |
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* Add back the dynamically-calculated register state |
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* size. |
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*/ |
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task_size += fpu_kernel_xstate_size; |
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/* |
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* We dynamically size 'struct fpu', so we require that |
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* it be at the end of 'thread_struct' and that |
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* 'thread_struct' be at the end of 'task_struct'. If |
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* you hit a compile error here, check the structure to |
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* see if something got added to the end. |
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*/ |
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CHECK_MEMBER_AT_END_OF(struct fpu, state); |
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CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu); |
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CHECK_MEMBER_AT_END_OF(struct task_struct, thread); |
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arch_task_struct_size = task_size; |
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} |
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/* |
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* Set up the user and kernel xstate sizes based on the legacy FPU context size. |
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* |
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* We set this up first, and later it will be overwritten by |
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* fpu__init_system_xstate() if the CPU knows about xstates. |
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*/ |
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static void __init fpu__init_system_xstate_size_legacy(void) |
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{ |
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static int on_boot_cpu __initdata = 1; |
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WARN_ON_FPU(!on_boot_cpu); |
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on_boot_cpu = 0; |
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/* |
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* Note that xstate sizes might be overwritten later during |
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* fpu__init_system_xstate(). |
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*/ |
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if (!boot_cpu_has(X86_FEATURE_FPU)) { |
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fpu_kernel_xstate_size = sizeof(struct swregs_state); |
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} else { |
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if (boot_cpu_has(X86_FEATURE_FXSR)) |
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fpu_kernel_xstate_size = |
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sizeof(struct fxregs_state); |
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else |
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fpu_kernel_xstate_size = |
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sizeof(struct fregs_state); |
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} |
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fpu_user_xstate_size = fpu_kernel_xstate_size; |
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} |
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/* |
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* Find supported xfeatures based on cpu features and command-line input. |
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* This must be called after fpu__init_parse_early_param() is called and |
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* xfeatures_mask is enumerated. |
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*/ |
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u64 __init fpu__get_supported_xfeatures_mask(void) |
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{ |
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return XFEATURE_MASK_USER_SUPPORTED | |
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XFEATURE_MASK_SUPERVISOR_SUPPORTED; |
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} |
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/* Legacy code to initialize eager fpu mode. */ |
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static void __init fpu__init_system_ctx_switch(void) |
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{ |
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static bool on_boot_cpu __initdata = 1; |
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WARN_ON_FPU(!on_boot_cpu); |
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on_boot_cpu = 0; |
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} |
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/* |
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* Called on the boot CPU once per system bootup, to set up the initial |
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* FPU state that is later cloned into all processes: |
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*/ |
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void __init fpu__init_system(struct cpuinfo_x86 *c) |
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{ |
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fpu__init_system_early_generic(c); |
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/* |
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* The FPU has to be operational for some of the |
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* later FPU init activities: |
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*/ |
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fpu__init_cpu(); |
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fpu__init_system_generic(); |
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fpu__init_system_xstate_size_legacy(); |
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fpu__init_system_xstate(); |
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fpu__init_task_struct_size(); |
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fpu__init_system_ctx_switch(); |
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}
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